Semiconductor photoelectrodes used in liquid electrolytes are known. These photoelectrodes can be prepared from various elemental and compound semiconductors, such as silicon and indium phosphide. The photoelectrode is immersed in an electrolyte and a photovoltage is produced when light falls on the photoelectrode.
The electrolyte contributes to the deterioration of photoelectrode performance over time. The deterioration is particularly prevalent with photoelectrodes formed from a semiconducting material, such as silicon, that naturally forms an oxide layer. It is believed that current flow in n-type silicon photoelectrodes stimulates oxide growth when holes recombine at the oxide-electrolyte interface. The increased oxide thickness adds resistance to the electrode circuit resulting in performance deterioration. The same result will occur with photoelectrodes prepared from other semiconducting materials on which an oxide layer naturally forms or upon which a transparent oxide is deposited for protective or optical purposes.